JPH10140244A - Production of grain oriented electrical steel sheet excellent in lower magnetic field iron loss characteristic in comparison with high magnetic field iron loss characteristic - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the iron loss characteristic in a low magnetic field by controlling a slab heating temp., Al content and the combination of a hot-rolled sheet annealing temp. and decarburizing annealing temp. SOLUTION: In order to reduce the iron loss, secondary recrystallized grain is necessary to fine. For this purpose, the content of Al as an inhibitor component is made to in the range of 0.010-0.020wt.%. The steel adjusted with the component in such a way, is heated on the slab and this slab heating temp. is made to <=1250 deg.C. By this method, the good crystal grain distribution and the magnetic characteristics can be obtd. The slab in such a way, is hot-rolled, and successively, after applying the annealing to the hot-rolled sheet, cold-rolling is executed and further, the decarburize-annealing is executed. In order to fine the secondary recrystallized grain, the hot-rolled sheet annealing temp. x ( deg.C) and the decarburized annealing temp. y ( deg.C) are regulated so as to satisfy the following relations. 800<=x<=1000 and (-x/2)+1200<=y<=(-x/2)+1300.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a grain-oriented electrical steel sheet, and more particularly to a grain-oriented electrical steel sheet having a low magnetic field iron loss characteristic superior to a high magnetic field iron loss characteristic used for an iron core or an EI core of a small generator. The present invention relates to a method for manufacturing a grain-oriented electrical steel sheet requiring characteristics.

[0002]

2. Description of the Related Art Grain-oriented electrical steel sheets are mainly used as iron core materials for transformers and other electrical equipment. In this case, a characteristic required for the grain-oriented electrical steel sheet is that iron loss represented by W17 / 50 (W / kg), which is a loss when magnetized to 1.7 T at a frequency of 50 Hz, is generally low. is important. Therefore, much research has been conducted to reduce W17 / 50, and in order to suppress the hysteresis loss, the crystal orientation of the product sheet is integrated as much as possible in the {110} <001> orientation where the easy magnetization axis <001> is aligned with the rolling direction. Techniques have been disclosed.

[0003] As a general method of manufacturing a grain-oriented electrical steel sheet, a slab having a thickness of 100 to 300 mm is heated to a high temperature and then hot-rolled, and then the hot-rolled sheet is subjected to one or two or more cold treatments including intermediate annealing. The final thickness by cold rolling, after decarburizing annealing, a complex process of performing a final finish annealing for the purpose of secondary recrystallization and purification after applying an annealing separating agent has been taken, during the final finish annealing $ 11 by secondary recrystallization
Crystal grains of 0 ° <001> orientation are grown.

[0004] In order to effectively promote such secondary recrystallization, it is important to first disperse a dispersed phase called an inhibitor that suppresses the growth of primary recrystallization into a uniform and appropriate size. Representative examples of such inhibitors include sulfides such as MnS, MnSe, AlN, and VN, Se compounds, nitrides, and the like, which have extremely low solubility in steel.

[0005] As a method for appropriately controlling the above-mentioned inhibitor mainly composed of sulfide, Se compound and nitride, in the conventional process, the inhibitor is once completely solid-dissolved during slab heating before hot rolling. Sometimes precipitation methods have been used. In this case, the slab heating temperature for sufficiently dissolving the inhibitor is about 1400 ° C., which is about 200 ° C. higher than the slab heating temperature of ordinary steel. Such high-temperature slab heating has the following disadvantages. 1) The unit energy consumption is high due to high-temperature heating. 2) Melt scale is easily generated and slab dripping is easily generated. 3) Excessive decarburization of the slab surface layer occurs.

In order to solve the above problems 2) and 3),
An induction heating furnace dedicated to grain-oriented electrical steel sheets was devised, but the problem of increased energy costs remained. In particular, with the recent energy crisis, energy saving has become an urgent issue, and many researchers have made great efforts to achieve a lower slab heating temperature.

For example, in Japanese Patent Publication No. 54-24687, steel contains grain boundary segregation elements such as As, Bi, and Sb.
A method has been disclosed in which the slab heating temperature is adjusted to a range of 1050 to 1350 ° C. by using it as an inhibitor. In Japanese Patent Application Laid-Open No. 57-158332, the slab heating temperature is lowered by lowering the Mn content and the ratio of Mn / S to 2.5 or less, and the addition of Cu stabilizes the secondary recrystallization. A technique for doing so has been disclosed. JP 5
JP-A-7-89433 discloses that in addition to Mn, S, Se, S
b, Bi, Pb, B, and other elements, and adding the columnar crystal ratio of the slab and the secondary cold rolling reduction to 11
A lower slab heating temperature of 00 to 1250 ° C. is realized. However, these are technologies that do not use AlN, which has a very low solubility in steel, as an inhibitor. Therefore, the inhibitory power of the inhibitor is weak, the magnetic properties are now one step worse, or the technology is limited to laboratory-scale technology. was there.

Japanese Unexamined Patent Publication (Kokai) No. 59-190324 discloses a novel technique of performing pulse annealing at the time of primary recrystallization annealing, but this is also limited to a laboratory scale manufacturing means. In JP-A-59-56522, Mn is set to 0.0
A technique for lowering the slab heating temperature by reducing the S content to 8 to 0.45% and the S content to 0.007% or less is disclosed. Further, Japanese Patent Application Laid-Open No. 59-190325 discloses a secondary recycling method in which Cr is added. Techniques for stabilizing crystals have been disclosed. These are characterized by lowering the amount of S to achieve solid solution of MnS during slab heating. However, according to these techniques, there is a problem in that a coil having a large weight causes variations in magnetic characteristics in the width direction and the longitudinal direction.

Japanese Patent Application Laid-Open No. 57-207114 discloses a technique that combines a very low carbon composition (C: 0.002 to 0.010%) and a low slab heating temperature. This technique is based on the idea that, when the slab heating temperature is low, it is more advantageous not to pass through the austenite phase between solidification and hot rolling in subsequent secondary recrystallization, but the amount of C is extremely high. Although low is also advantageous for preventing breakage during cold rolling, it is necessary to perform nitriding during decarburization annealing in order to stabilize secondary recrystallization.

[0010] In response to this technology, many technical developments have been made on the premise of nitriding. That is, JP-A-62-70
Japanese Patent Application Laid-Open No. 521 discloses a technique for specifying low-temperature slab heating by specifying the conditions of the final annealing and nitriding in the middle of the final annealing. Further, Japanese Patent Application Laid-Open No. 62-40315 does not dissolve the slab at the time of slab heating. A method has been disclosed that contains amounts of Al and N and controls the inhibitor to an appropriate state by nitridation during the process. However, the method of performing nitriding in the middle of decarburizing annealing requires new equipment and increases costs, and also has a problem that nitriding during finish annealing is difficult to control.

On the other hand, in recent years, it has become a problem that the iron loss characteristics of materials do not always match the iron loss characteristics of actual machines. Certainly, the iron loss of the iron core and the wound iron core of the large transformer is such that a material having a low value of W17 / 50 has excellent characteristics of the actual machine. However, in the case of an iron core of a small generator or an EI core which is a small transformer, there is a problem that the value of W17 / 50 of the material does not match the characteristics of the actual machine due to the complicated magnetic flux flowing inside the steel sheet. In recent years, along with the progress of the energy crisis, reduction of energy wasted in transformers has been required, and efforts have been made to reduce iron loss in actual machines. At present, it is often difficult to select materials.

In general, in order to reduce iron loss of a material, a method of increasing electric resistance by containing Si effective to reduce eddy current loss, a method of reducing the thickness of a steel sheet, a method of reducing a crystal grain size, There is known a method of improving the magnetic flux density by increasing the degree of integration of the crystal orientation into {110} <001>. Among them, a method for improving the magnetic flux density has been well studied. For example, Japanese Patent Publication No. 51-2290 discloses a method of adding Al as an inhibitor component in steel at 1300 ° C.
A technique of performing slab heating at the above high temperature, performing hot rolling finish rolling in a short time at a high temperature, and performing hot rolling at a hot rolling end temperature of 980 ° C. or more is disclosed in Japanese Patent Publication No. 46-23820. Al after addition to hot rolling after 1000 to 1200
A technique is disclosed in which fine AlN is precipitated by high-temperature hot-rolled sheet annealing at a high temperature of ℃ and quenching accompanying the same, and a high pressure of 80 to 95% is applied, whereby an extremely high magnetic flux density of 1.95 T for B10 is obtained. A material with low iron loss has been obtained.

However, in the method of aligning crystal orientations and improving the magnetic flux density, which has conventionally been pursued when W17 / 50 is reduced, the iron loss characteristics of the EI core and the iron core of the small generator are improved. Was not effective. The reason is that the magnetic flux flowing inside the steel plate is complicated in the EI core and the like.

As a means for reducing iron loss, a method of increasing the Si content, a method of reducing the thickness of the steel sheet, and a method of reducing the crystal grain size have been examined as alternatives to the method of improving the magnetic flux density.
Among them, the method of increasing the Si content is not preferable because excessive addition of Si deteriorates the rolling property and workability of the steel sheet, and the method of reducing the thickness of the steel sheet also causes an extreme increase in manufacturing cost. was there.

Separately from this, a better index for material evaluation was examined for iron loss of the iron core of the actual small generator and iron loss of the EI core. Iron loss characteristics in a low magnetic field as compared with the characteristics, that is, W10 / 50 (iron loss at a magnetic flux density of 1.0 T: W
/ Kg) with respect to W17 / 50 and the characteristics of the actual machine had a good correlation. The reason for this is that in the case of the actual machine, the distribution of magnetic flux flowing in the steel sheet is not uniform, so iron loss in a low magnetic field is more important. It is considered that the iron loss of the actual machine is reduced as a result of improvement in the direction of more uniformity.

[0016]

[Table 1]

Investigations were made on the materials a and b having such good actual machine characteristics, and it was found that the crystal structure was fine. Even though there is a knowledge that smaller crystal grain size is more advantageous for reducing iron loss,
This is a study on reduction of 17/50, and is aimed at improving the characteristics of actual equipment such as reducing iron loss of EI cores, that is, W1.
W10 / 50 and W17 of W10 / 50 increased by 7/50
From the viewpoint of reducing the ratio to / 50, there is no study on what size and distribution the crystal grain size should be controlled, and the proper distribution of the crystal grains has not been clarified.

Incidentally, a technique for controlling the crystal grain size of grain-oriented electrical steel sheets, which has been widely known, is disclosed in, for example,
No. 9-20745 discloses an average crystal grain size of 1 to 6 mm.
And Japanese Patent Publication No. Sho 62-56923 discloses a method for reducing the iron loss by setting the number ratio of crystal grains of 2 mm or less to 15 to 70%. Furthermore, Japanese Patent Publication No. 6-80172 discloses a technique for reducing iron loss by allowing fine grains of 1.0 mm or more and 2.5 mm or less to exist in a mixed state. However, these are all aimed at the value W17 / 50 of the high magnetic field iron loss of the magnetic flux density of 1.7 T, and have not been studied about the iron loss in the low magnetic field region.

To summarize the above, in the prior art, 1) In order to increase the degree of collection of the crystal orientation to {110} <001> and improve the magnetic flux density, it is necessary to perform high-temperature slab heating at about 1400 ° C. In addition, nitridation is required on the way. 2) However, the method of extremely increasing the degree of integration of the crystal orientation into {110} <001> is not effective in improving the iron loss characteristics of the EI core and the iron core of the actual machine of the small generator. There was a problem.

[0020]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method for producing a grain-oriented electrical steel sheet which is more excellent in low-field iron loss characteristics than high-field iron loss characteristics suitable for an EI core or the like. Is to provide. In addition, slab heating is performed at the same temperature as ordinary steel, and especially without aggressive nitriding,
An object of the present invention is to provide a method for manufacturing a grain-oriented electrical steel sheet suitable for an EI core, a small generator, and the like. In other words, it is an object of the present invention to provide a technology for producing a grain-oriented electrical steel sheet having excellent low-field iron loss characteristics with low energy consumption and without complicating the process.

[0021]

SUMMARY OF THE INVENTION The inventors of the present invention have, after intensive studies, increased W17 / 50 and reduced W10 / 50, that is, reduced the value of the ratio of W10 / 50 to W17 / 50. In order to do so, it was newly found that the slab heating temperature should be reduced, the Al content as an inhibitor should be controlled, and the hot-rolled sheet annealing temperature and the decarburization annealing temperature should be controlled in combination. . Specifically, first, Si: 2.0 to 4.5% and C: 0.02 to 2.0% by weight.
0.07%, Mn: 0.03 to 2.5%, and Al: 0.010 to 0.020 as an inhibitor component
%, Sb: 0.0010 to 0.080%, heated, hot-rolled, then hot-rolled, annealed, cold-rolled to a final thickness, and then removed. Charcoal annealing,
Further, in the method for producing a grain-oriented electrical steel sheet in which finish annealing is performed after applying an annealing separator, the heating temperature of the steel slab is set to 1
250 ° C. or lower, hot rolled sheet annealing temperature x ° C. and decarburization annealing temperature y ° C. are set to 800 ≦ x ≦ 1000 and (−x / 2) + 1200 ≦ y ≦ (−x / 2) +1300, and Manufacture of grain-oriented electrical steel sheets having excellent low-field iron loss characteristics compared to high-field iron loss characteristics, wherein cold rolling is performed by a tandem rolling mill at a rolling reduction of 80% or more and 95% or less. Suggest a method.

Further, Mo, B
i, Te, Nb, Sn, and Cr are contained, and the contents of Al and N in the steel slab are set to 1.67 ≦ Al (wt%) / N (wt%) ≦ 2.18. Further, the cold rolling is performed by a tandem rolling mill at a rolling reduction of 80% or more and 95% or less and at a temperature of 90 ° C or more, preferably 120 ° C or more and 180 ° C or less, so that the directional electromagnetic processing according to the present invention can be achieved. It enables the production of steel sheets.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, various experiments leading to the completion of the present invention will be described, and embodiments of the present invention will be described in detail. (Experiment 1) Preliminary Experiment Two slabs of ingot symbols VI and XI shown in Table 2 were prepared, one at 1200 ° C and the other at 1400 ° C.
, And hot-rolled to form a 2.0 mm hot-rolled coil. Then these coils were all split into two parts, one of which was 90
The hot rolled sheet was annealed at 0 ° C. for 60 seconds and the other at 1050 ° C. for 60 seconds. In addition, these coils are
The thickness was reduced to 0.34 mm by a tandem rolling mill at a temperature of ° C. Thereafter, a degreasing treatment is performed, decarburizing annealing is performed at 830 ° C. for 2 minutes, an annealing separating agent is applied to the coil surface, and the temperature is raised to 600 ° C. in an atmosphere of N ₂ alone, and then to 1050 ° C., 25% N ₂ . A final finishing annealing was performed in a mixed atmosphere of 75% H ₂ and thereafter in a single atmosphere of H _2, which was heated to 1200 ° C. and maintained for 5 hours, after which the unreacted separating agent was removed.

[0024]

[Table 2]

[0025]

[Table 3]

These steel sheets were macro-etched and the shape of secondary grains was observed. These coils were further coated with an insulating coating mainly composed of magnesium phosphate containing 40% colloidal silica and baked at 800 ° C. to obtain products. A specimen of Epstein size was cut out from each product along the rolling direction and subjected to strain relief annealing at 800 ° C. for 3 hours, and then the values of iron loss at 1.0 T and 1.7 T of magnetic flux density, W10 / 50, W17 / 50 and magnetic flux density B8
Was measured. These values are summarized in Table 3. Further, an EI core was manufactured by punching an iron core for the EI core from each product, performing strain relief annealing, stacking, winding a copper wire, and the like. Table 3 also shows the iron loss characteristics of these cores.

As shown in Table 3, the ratio of W10 / 50 to W17 / 50 was small, and only the sample had good iron loss of the EI core. After finishing annealing the sample plate,
There is no defective part of secondary recrystallization by macro etching, and
There were almost no coarse particles having a particle size exceeding 7 mm. Al
In the case of steel symbol XI having an amount of 0.025 wt%, slab heating 12
At 00 ° C., secondary recrystallization failure occurred (sample, see). This is presumably because AlN hardly dissolved in the solution before hot rolling. On the other hand, slab heating temperature 1400 ° C
Sample, the secondary recrystallization was sufficient, and B8, W17 / 5
0 showed good values, but the iron loss of the EI core was large. Looking at the macrostructure after finish annealing, the sample,
In this case, the secondary grains became 20 mm or more and were very coarse.

In the sample, secondary recrystallization failure occurred partially, and the size of the secondary recrystallized grains was about 10 mm. In the sample, there was no defective secondary recrystallization, and the particle size of the secondary particles was about 10 to 15 mm. As for the reason that the iron loss of the EI core was good only for the sample, A
It is considered that the lowering of the amount of l and the lowering of the slab heating temperature made the inhibitor inhibitory force more appropriate. In other words, the slab heating temperature is increased and Al
The method of increasing the amount is to increase B8 conventionally and to increase W17 /
A method that has been adopted as a method of lowering 50 is
From the viewpoint of reducing the iron loss of the I core, the secondary grains are too large, which is not preferable. That is, if the inhibitory force of the inhibitor is too strong, only a small number of grains very close to the (110) [001] orientation undergo secondary recrystallization, so that the secondary particle size becomes too coarse.

From the results of this preliminary experiment, it was found that the higher the temperature of the hot-rolled sheet annealing, the larger the grain size after primary recrystallization. The primary particle size affects the driving force for grain growth during secondary recrystallization. However, from experiments, in the case of low-temperature slab heating and low Al, a hot-rolled sheet for producing appropriate secondary recrystallization is used. The annealing temperature was found to be relatively low. As a factor for changing the primary particle size, a decarburizing annealing temperature is considered in addition to the hot-rolled sheet annealing temperature. Therefore,
Next, the influence of the decarburizing annealing temperature and the effect of the hot-rolled sheet annealing temperature were examined by the following experiment 2.

(Experiment 2) Influence of hot rolled sheet annealing temperature and decarburizing annealing temperature A slab of steel ingot symbol VI shown in Table 2 was heated at 1200 ° C., and then hot-rolled to obtain a 2.4 mm hot-rolled coil. And
These hot-rolled coils were subjected to hot-rolled sheet annealing for 60 seconds, pickled, and then hot-rolled to a thickness of 0.34 mm by a tandem rolling mill at a temperature of 100 to 160 ° C. Thereafter, a degreasing treatment is performed, decarburization annealing is performed for 120 seconds, an annealing separator is applied, and the temperature is raised to 500 ° C. in an atmosphere of N ₂ alone, up to 850 ° C., a mixed atmosphere of 25% N ₂ and 75% H ₂ , Thereafter, final finishing annealing was performed in which the temperature was raised to 1180 ° C. in an atmosphere of H ₂ alone, and then the unreacted separating agent was removed. These coils were further coated with an insulating coating mainly composed of magnesium phosphate containing 40% of colloidal silica and baked at 800 ° C. to obtain products. In addition, punching iron cores for EI cores from each product, performing strain relief annealing,
The EI core was manufactured by stacking, winding a copper wire, and the like.

The hot-rolled sheet annealing temperature is 750 ° C. to 1050 ° C.
FIG. 1 shows the results obtained by changing the decarburization annealing temperature from 690 ° C. to 900 ° C. and examining the relationship with the iron loss W17 / 50 of the EI core. From FIG. 1, the range in which the iron loss value of the EI core is good is 800 ≦ x ≦ 1000 and (−x / 2) + 1200 ≦ y ≦ (−x / 2) +1300 x: hot rolled sheet annealing temperature ( ° C), y: decarburizing annealing temperature (° C).

The higher the temperature of both the hot-rolled sheet annealing temperature and the decarburization annealing temperature, the larger the grain size after primary recrystallization. In order to reduce the iron loss value of the EI core, it is considered necessary to make the secondary recrystallized grains finer. However, in order to make the secondary grains finer, it is necessary to appropriately control the primary grains. . Experiment 2 shows that the hot rolled sheet annealing temperature x and the decarburization annealing temperature y should be within the above-mentioned inequalities for proper control of the primary grains.
I knew from The range that satisfies the above inequality is characterized in that it is in a low temperature range as compared with a normal method for manufacturing a grain-oriented electrical steel sheet.

(Experiment 3) Examination of rolling method of cold rolling Four slabs of steel symbol VI shown in Table 2 were set at 1150 ° C.
And then hot rolled to form a 2.4 mm hot rolled coil.
These hot-rolled coils were annealed at 900 ° C. for 30 seconds, pickled, and then cold-rolled to a thickness of 0.34 mm. At this time, the first coil is at 120 to 180 ° C.
The second coil was also subjected to warm rolling by a tandem rolling mill at a temperature of, and the second coil was similarly rolled at a steel sheet temperature of 50 to 80 ° C by spraying a large amount of rolling coolant onto the surface of the steel sheet using a tandem rolling mill. The coil of No. is subjected to aging treatment at a temperature of 150 to 220 ° C. between rolling passes by a reverse type rolling mill, and the fourth coil is similarly supplied with a large amount of coolant by a reverse type rolling mill, and is heated to a temperature of 50 to 80 ° C. Was rolled. After that, each coil is degreased to 8
Perform decarburization annealing at 00 ° C for 2 minutes, apply an annealing separating agent to the coil surface, and raise the temperature up to 700 ° C in an atmosphere of N ₂ alone,
A mixed atmosphere of thereafter up to 850 ℃ 25% N ₂ and 75% H _2, subjected to final finish annealing and holding for 5 hours after heating to 1180 ° C. in the subsequent H ₂ alone atmosphere, and then remove unreacted separating agent. These coils were further coated with an insulating coating mainly composed of magnesium phosphate containing 60% of colloidal silica and baked at 800 ° C. to obtain products.

A test piece of Epstein size was cut out from each product along the rolling direction, subjected to strain relief annealing at 800 ° C. for 3 hours, and then the value of iron loss W10 / 50 at a magnetic flux density of 1.0T and 1.7T. , W17 / 50 and magnetic flux density B8 were measured. These values are summarized in Table 4. Further, an EI core was manufactured by punching out an iron core for the EI core from each product, performing strain relief annealing, stacking, winding a copper wire, and the like. Table 4 also shows these iron loss characteristics.

[0035]

[Table 4]

As shown in Table 4, a product having a good low-field iron loss as compared with the iron loss at a high magnetic field was obtained only in the first and second coils rolled using a tandem rolling mill. In particular, the actual characteristics of the first coil that was warm-rolled at 120 to 180 ° C. were excellent.

In general, warm rolling or aging has the function of changing the rolling deformation texture of the crystal, and becomes the core of secondary recrystallization in the primary recrystallization structure after rolling recrystallization (110) [00].
1) It is known to increase the generation density of crystal grains in the orientation. For this purpose, as disclosed in Japanese Patent Publication No. 54-13846, it has conventionally been considered appropriate to promote the diffusion of C by aging treatment between rolling passes by a reverse type rolling mill in a Sendzimir mill. .

However, as shown in the results of this experiment, aging treatment between rolling passes was not effective, and rolling by a tandem rolling mill was effective. Considering the difference between the two, in the former, the strain rate during rolling is relatively small,
Also, there is sufficient time between rolling passes, during which heat generated due to work strain inevitably causes static aging due to the diffusion phenomenon of C to dislocations, whereas the latter is the strain rate during rolling. Is relatively large, and the time between rolling passes is extremely short, so that static aging does not occur. During the rolling pass, dislocations are added and at the same time, dynamic strain aging due to diffusion of C into dislocations occurs. is there.

The results of this experiment show that the tandem rolling method is superior to the reverse rolling method, that the tandem warm rolling is superior to the low-temperature tandem rolling method, and that the aging between passes is harmful in the reverse rolling method. I have. Thus, high strain rates and dynamic aging are effective, whereas static aging has a detrimental effect. For this reason, in the present invention, it is desirable to adopt rolling in a tandem rolling mill and to set the rolling temperature to 90 ° C. or higher, preferably 120 ° C. or higher and 180 ° C. or lower.

(Experiment 4) Reexamination of Components From Experiment 1, it was found that reducing the Al content of the slab and lowering the slab heating temperature was effective in reducing the iron loss value of the EI core. Was. Since Al acts as an inhibitor as AlN, the content of N was reexamined.

The slabs of steel symbols IV to VIII shown in Table 2 were heated to 1150 ° C., and then hot-rolled to obtain hot-rolled coils having a thickness of 2.4 mm. Thereafter, hot-rolled sheet annealing was performed at 900 ° C. for 60 seconds, and after pickling, it was rolled at a temperature of 150 ° C. by a tandem rolling mill to a thickness of 0.34 mm. Thereafter, degreasing treatment is performed, decarburizing annealing is performed at 800 ° C. for 2 minutes, and after applying an annealing separating agent, an atmosphere of N ₂ alone is used up to 700 ° C. at the time of heating, and then 25% N ₂ and 75% H ₂ mixed atmosphere, was warmed to 1180 ° C. in the subsequent H ₂ alone atmosphere 5
A final finish anneal with a holding time was applied, after which the unreacted separating agent was removed. These coils were further coated with an insulating coating mainly composed of magnesium phosphate containing 60% of colloidal silica and baked at 800 ° C. to obtain products.

A test piece of Epstein size was cut out from each product along the rolling direction, subjected to strain relief annealing at 800 ° C. for 3 hours, and then the value of iron loss W10 / 50 at a magnetic flux density of 1.0T and 1.7T. , W17 / 50 and magnetic flux density B8 were measured. These values are summarized in Table 5. Further, an EI core was manufactured by punching an iron core for the EI core from each product, performing strain relief annealing, stacking, winding a copper wire, and the like. Table 5 also shows the iron loss characteristics of these cores.

[0043]

[Table 5]

According to Table 5, the value of Al / N was 27/14.
(= 1.93), that is, as the atomic ratio was closer to 1: 1, a better result was obtained. In AlN and ordinary grain-oriented electrical steel sheets used as inhibitors, Al has more atoms than N in the number of atoms. Thus, Al / N is 1:
The reason why a better result is obtained as the value is closer to 1 is considered as follows. In a normal grain-oriented electrical steel sheet, (11
0) Since high integration in the [001] orientation is required, at the time of finish annealing, the starting temperature of secondary recrystallization is increased, and (11)
0) Only grains having an orientation very close to [001] are subjected to secondary recrystallization. That is, in order to increase the temperature at which AlN completely dissolves and the deterrent is lost, the amount of Al is excessive. However, in the present invention, it is necessary to make the secondary grains finer and to reduce iron loss in an actual machine, even if the accumulation in (110) [001] is somewhat weak. Therefore, it is not necessary to contain Al excessively. However, it is not preferable that the inhibitor is too weak. In order to effectively utilize the inhibitory effect of AlN with a relatively small amount of Al, it is preferable to contain Al and N in equal amounts by the number of atoms.

Although the basic configuration of the present invention is clear from the above experimental results, embodiments will be specifically described below. First, the components will be described.

C: 0.02 to 0.07% The content of C is set to 0.07% or less. That is, 0.07%
Exceeds γ, the amount of γ transformation becomes excessive, the distribution of Al during hot rolling becomes non-uniform, and A precipitates during the heating process of hot-rolled sheet annealing.
The distribution of 1N is also non-uniform and good magnetic properties in a low magnetic field cannot be obtained. On the other hand, if the content is less than 0.02%, the effect of improving the structure cannot be obtained, and the secondary recrystallization becomes incomplete, and the magnetic properties also deteriorate. Therefore, C is limited to the range of 0.02 to 0.07%.

Si: 2.0 to 4.5% Si is an essential element for increasing electric resistance and reducing iron loss. For this purpose, it is necessary to contain 2.0% or more. If it exceeds 4.5%, the workability will deteriorate,
Since it becomes extremely difficult to manufacture an electromagnetic steel sheet and to process a product, the content is set to 2.0 to 4.5%.

Mn: 0.03 to 2.5% Mn is an element necessary for increasing electric resistance and improving hot workability at the time of production, similarly to Si. For this purpose, a content of 0.03% or more is necessary, but 2.5% or more is required.
%, The magnetic properties are degraded by inducing γ transformation, so that the content is set in the range of 0.03 to 2.5%.

Inhibitor component, Al: 0.010
0.020% In addition to these elements, the steel must contain an inhibitor component for inducing secondary recrystallization. First, it is necessary to contain 0.010 to 0.020% of Al. Here, if the Al content is less than 0.010%, the amount of AlN precipitated in the temperature rising process of hot-rolled sheet annealing becomes insufficient, and if it exceeds 0.020%, the low temperature of the slab at about 1200 ° C. The solid solution of AlN becomes difficult during heating, and the solid solution temperature of AlN rises, so that AlN precipitates in hot rolling and A in the temperature rising process of hot-rolled sheet annealing.
Fine precipitation of 1N becomes impossible, and good iron loss characteristics in a low magnetic field cannot be obtained. When slab heating is performed at a high temperature of around 1400 ° C to eliminate this defect, the crystal grain size of the product becomes coarse, iron loss in a high magnetic field decreases, and iron loss in a low magnetic field increases. Iron loss of actual machine deteriorates. Therefore, Al is set in the range of 0.010 to 0.020%.

Inhibitor component, Sb: 0.0010
0.080% Sb is also contained as an inhibitor. Sb has the effect of forming fine precipitates in hot rolling and increasing the precipitation nuclei of AlN in the temperature rising process of the hot-rolled sheet annealing in the next step. To obtain such an effect, 0.0010% or more is necessary. However, if the content exceeds 0.08%, mechanical properties such as bend characteristics of a product are deteriorated.
-0.080%.

N: 0.0030 to 0.0100% Further, N forms AlN and functions as an inhibitor. Therefore, it is necessary to contain 0.0030% or more of N. However, if the content exceeds 0.0100%, gasification occurs in the steel, causing defects such as blisters.
Must be in the range of 0030-0.0100%. It has already been mentioned that the Al / N ratio is preferably as close to 1 as possible.

Other additive elements: Mo, Bi, Te, N
Other elements such as b, Sn, and Cr are not necessarily required to obtain a grain-oriented electrical steel sheet having a good low-field iron loss property as compared to a high-field iron loss property. Mo addition has the effect of improving the surface properties of the steel sheet.
It is possible to appropriately contain i, Te, and the like. In addition, Nb, Sn,
It is also possible to contain Cr and the like.

(Slab Heating) The steel adjusted to the above components is usually subjected to slab heating and then hot-rolled into a hot-rolled coil. The slab heating temperature is set to 1250 ° C. or less. What is important in the invention is as described above. That is, when slab heating is performed at a high temperature, the crystal grains of the product are coarsened, and iron loss in a low magnetic field is deteriorated. Therefore, in order to obtain good crystal grain distribution and magnetic properties, the slab heating temperature must be 1250 ° C. or less. In recent years, a method of performing direct hot rolling after continuous casting without performing slab heating has been developed. However, since this method can lower the slab heating temperature, it can be suitably carried out in the present invention.

(Hot Rolling, Cold Rolling) Next, the hot rolled coil is subjected to hot rolled sheet annealing, pickling, cold rolling, and then decarburizing annealing also serving as primary recrystallization annealing. In the cold rolling, the final thickness is obtained by one rolling using a tandem rolling mill. In this case, the final thickness is obtained by one cold rolling, but it is an essential condition to perform rolling by a tandem rolling mill. Here, a tandem rolling mill refers to a rolling mill that passes between roll pairs and is continuously arranged in a rolling direction in a rolling direction to enable continuous rolling with respect to a flow of a steel sheet. . It is considered in Experiment 3 that rolling by such a tandem rolling mill can suppress harmful static strain aging between rolling passes and increase strain rate to obtain a good rolling texture. It is clear from As a result, the primary recrystallization texture is improved in such a direction as to promote the grain growth of the secondary recrystallization, and nucleation and growth of fine crystal grains are promoted. In this respect, it is inevitably accompanied by static aging, resulting in a primary recrystallized structure inferior in the growth property of secondary recrystallized grains, which is different from the case of a reverse method such as a Sendzimir rolling mill in which poor secondary recrystallization occurs. .

(Warm Rolling, Rolling Reduction) In the tandem rolling, it is possible to raise the temperature of the steel sheet during rolling to cause dynamic strain aging and obtain a more preferable effect. The rolling temperature for this purpose is 90 ° C. or more and 300 ° C. or less, preferably 120 ° C. or more and 180 ° C.
The following are appropriate: In the present invention, the rolling reduction of the cold rolling is set to 80% or more and 95% or less. The same applies to the case of warm rolling. If the rolling reduction is less than 80%, the grain size of the product becomes coarse, and the low-field iron loss increases in spite of the reduction in the high-field iron loss. Conversely, if the rolling reduction exceeds 95%, secondary recrystallization failure occurs.

(Hot Rolled Sheet Annealing and Decarburizing Annealing) In hot rolled sheet annealing and decarburizing annealing, as shown in Experiment 2, the hot rolled sheet annealing temperature x (° C.) and the decarburizing annealing temperature y (° C.) 800 ≦ x ≦ 1000 and (−x / 2) + 1200 ≦ y ≦ (−x / 2) +1300.

(Final Finish Annealing, Coating) After decarburizing annealing, an annealing separator is applied and final finish annealing is performed. It is necessary to suppress nitriding during decarburizing annealing and final finishing annealing as much as possible. After the final annealing, an insulation coating is applied and baked if necessary, and further flattening anneal is performed to obtain a product.

[0058]

【Example】

Example 1 A molten steel having a composition of ingots I to XI shown in Table 2 was formed into a slab by continuous casting while applying electromagnetic stirring, heated to 1200 ° C., and then hot-rolled to 2.4 mm.
Hot-rolled coil of thickness. Next, at 880 ° C
For 60 seconds. Further, these coils were rolled to a thickness of 0.34 mm by a tandem rolling mill at a temperature of 150 ° C. after pickling. Thereafter, a degreasing treatment is performed, decarburization annealing is performed at 820 ° C. for 2 minutes, an annealing separator is applied to the coil surface, and the temperature is raised to 500 ° C. in an atmosphere of N ₂ alone, and then to 1050 ° C. in 25% N ₂ . A final finishing annealing was performed in a mixed atmosphere of 75% H ₂ and thereafter in a single atmosphere of H _2, which was heated to 1200 ° C. and maintained for 5 hours, after which unreacted separating agent was removed. These coils were further coated with an insulating coating mainly composed of magnesium phosphate containing 40% of colloidal silica and baked at 800 ° C. to obtain products.

A test piece of Epstein size was cut out from each product along the rolling direction and subjected to strain relief annealing at 800 ° C. for 3 hours, and then the value of the iron loss W10 / 50 at a magnetic flux density of 1.0T and 1.7T. , W17 / 50 and magnetic flux density B8 were measured. These values are summarized in Table 6. Further, an EI core was manufactured by punching an iron core for the EI core from each product, performing strain relief annealing, stacking, winding a copper wire, and the like. Table 6 also shows the iron loss characteristics of these cores. As shown in Table 6, the grain-oriented electrical steel sheet using the steel slab within the composition range of the present invention is superior in iron loss characteristics in a low magnetic field as compared with the iron loss characteristics in a high magnetic field. Is extremely good.

[0060]

[Table 6]

[0061]

Example 2 A slab having the ingot symbol IX shown in Table 2 was used for 1150, 1200, 1250, 1300, 1
After being heated to each temperature of 350 ° C., hot rolling was performed to obtain a hot-rolled coil having a thickness of 2.4 mm. Next, 6 minutes at 880 ° C
Hot rolling annealing was performed for 0 second. Further, these coils were pickled at a temperature of 150.degree.
mm. Thereafter, degreasing is performed and 800
Decarburizing annealing at 2 ° C. for 2 minutes, applying an annealing separating agent to the coil surface, increasing the temperature to 500 ° C. in an atmosphere of N ₂ alone, and then up to 1050 ° C. in a mixed atmosphere of 25% N ₂ and 75% H ₂ Thereafter, a final finish annealing was performed in which the temperature was raised to 1200 ° C. for 5 hours in an atmosphere of H ₂ alone, and then the unreacted separating agent was removed. These coils were further coated with an insulating coating mainly composed of magnesium phosphate containing 40% of colloidal silica and baked at 800 ° C. to obtain products.

A test piece of Epstein size was cut out from each product along the rolling direction, subjected to strain relief annealing at 800 ° C. for 3 hours, and then the value of iron loss W10 / 50 at a magnetic flux density of 1.0 T and 1.7 T. , W17 / 50 and magnetic flux density B8 were measured. These values are summarized in Table 7. Furthermore, an EI core was manufactured by punching an iron core for the EI core from each product, performing strain relief annealing, stacking, and winding a copper wire. Table 7 also shows the iron loss characteristics of these cores. As shown in Table 7, the slab heating temperature was 125
When the temperature is 0 ° C. or lower, the iron loss characteristics in a low magnetic field are superior to the iron loss characteristics in a high magnetic field, and the iron loss value of an actual machine is extremely good.

[0063]

[Table 7]

[0064]

Example 3 A slab having the composition of steel ingot VII shown in Table 2 was heated at 1180 ° C. and then hot-rolled to 2.4 mm.
Hot-rolled coil of thickness. Next, the hot-rolled coil was subjected to hot-rolled sheet annealing for 60 seconds, and after pickling, was rolled to a thickness of 0.34 mm by a tandem rolling mill at a temperature of 80 ° C. afterwards,
After degreasing and decarburizing annealing for 2 minutes, an annealing separator is applied to the coil surface, and the temperature is raised to 500 ° C. in an atmosphere of N ₂ alone, and then up to 1050 ° C. in an atmosphere of 25% N ₂ and 75% H ₂ . A final finishing annealing was performed in which the temperature was raised to 1200 ° C. in a mixed atmosphere and thereafter in an atmosphere of H ₂ alone for 5 hours, and then the unreacted separating agent was removed. Here, the hot rolled sheet annealing temperature x ° C. and the decarburization annealing temperature y ° C. are (x, y) = (750, 800), (800, 75).
0), (800, 850), (800, 950), (9
00, 750), (900, 800), (900, 85)
0), (1000, 750), (1000, 800),
(1000, 850) and (1050, 800) were changed to 11 conditions. These coils were further coated with an insulating coating mainly composed of magnesium phosphate containing 40% of colloidal silica and baked at 800 ° C. to obtain products.

A test piece of Epstein size was cut out from each product along the rolling direction, subjected to strain relief annealing at 800 ° C. for 3 hours, and then the value of the iron loss W10 / 50 at a magnetic flux density of 1.0T and 1.7T. , W17 / 50 and magnetic flux density B8 were measured. These values are summarized in Table 8. Further, an EI core was manufactured by punching an iron core for the EI core from each product, performing strain relief annealing, stacking, winding a copper wire, and the like. Table 8 also shows the iron loss characteristics of these cores. As shown in Table 8, when the relationship between x and y is in the range of 800 ≦ x ≦ 1000 and (−x / 2) + 1200 ≦ y ≦ (−x / 2) +1300, iron in a high magnetic field The iron loss characteristics in a low magnetic field are superior to the loss characteristics, and the iron loss value of the actual machine is extremely good.

[0066]

[Table 8]

[0067]

Example 4 Molten steel having the composition of ingot symbol V shown in Table 2 was cast into a slab by a continuous casting machine while applying electromagnetic stirring. Seven slabs were heated at 1230 ° C. and then hot-rolled to obtain (a) 2.0 mm, (b) 2.2 mm, and (c).
2.5 mm, (d) 2.7 mm, (e) 3.2 mm,
(F) A hot-rolled coil having a thickness of 3.6 mm and (g) a thickness of 13 mm. Then, hot rolled sheet annealing is performed at 900 ° C for 30 seconds.
After pickling, it was rolled to a thickness of 0.49 mm by cold rolling. Therefore, the rolling reduction of the coil of (a) is 76%,
The rolling reduction of the coil of (b) is 78%, the rolling reduction of the coil of (c) is 80%, the rolling reduction of the coil of (d) is 82%,
The rolling reduction of the coil of (e) is 85%, the rolling reduction of the coil of (f) is 86%, and the rolling reduction of the coil of (g) is 96%. During these rollings, the rolling is performed at a coil temperature of 120 to 1 mm.
The temperature was set to 80 ° C., and rolling was performed by a tandem rolling mill. Thereafter, each coil is subjected to a degreasing treatment, subjected to decarburizing annealing at 840 ° C. for 2 minutes, an annealing separator is applied to the coil surface, and the temperature is raised to 700 ° C. in an atmosphere of N ₂ alone.
Until 50 ° C, final finishing annealing was performed in a mixed atmosphere of 25% N ₂ and 75% H ₂ , followed by heating to 1200 ° C in a single atmosphere of H _{2 for} 5 hours and then removing the unreacted separating agent. These coils were further coated with an insulating coating mainly composed of magnesium phosphate containing 60% of colloidal silica and baked at 800 ° C. to obtain products.

From each product, test pieces of Epstan size were cut out along the rolling direction and subjected to strain relief annealing at 800 ° C. for 3 hours, and then the values of iron loss at magnetic flux densities of 1.0 T and 1.7 T, W10 / 50, W17 / 50 and magnetic flux density B8 were measured. These values are summarized in Table 9. Further, an EI core was manufactured by punching an iron core for the EI core from each product, performing strain relief annealing, stacking, winding a copper wire, and the like. Table 9 also shows the iron loss characteristics of these cores. As shown in Table 9, the rolling reduction of the cold rolling was 8
A grain-oriented electrical steel sheet satisfying the constituent requirements of the present invention of 0% or more and 95% or less has excellent iron loss characteristics in a low magnetic field as compared with the iron loss characteristics in a high magnetic field, and has an extremely good iron loss value of a real machine. It is.

[0069]

[Table 9]

[0070]

As described in detail above, according to the manufacturing method of the present invention, a grain-oriented electrical steel sheet having excellent low-field iron loss characteristics as compared with high-field iron loss characteristics can be reliably obtained. EI
A product with excellent characteristics of the actual machine such as a core can be obtained,
Since the heating temperature of the electromagnetic steel sheet slab can be greatly reduced, it greatly contributes to energy saving.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the iron loss value of an EI core and the annealing temperature of a hot-rolled sheet and the decarburization annealing temperature.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Atsuto Honda 1-chome, Kawasaki-dori, Mizushima, Kurashiki-shi, Okayama Pref. 1-chome (without address) Inside Kawasaki Steel Corporation Mizushima Works

Claims (5)

[Claims] 1. The composition contains, by weight%, Si: 2.0 to 4.5% C: 0.02 to 0.07% Mn: 0.03 to 2.5%, and Al: 0.010 as an inhibitor component. After heating a steel slab containing ０．０0.020% Sb: 0.0010 to 0.080%, hot rolling is performed, then hot-rolled sheet annealing is performed, and then the final thickness is reduced by cold rolling. A method for producing a grain-oriented electrical steel sheet in which a decarburizing annealing and an annealing separator are applied and finish annealing is performed, wherein the heating temperature of the steel slab is 1250 ° C. or less. The temperature is set to 800 ≦ x ≦ 1000 and (−x / 2) + 1200 ≦ y ≦ (−x / 2) +1300, and the cold rolling is performed by a tandem rolling mill at a draft of 80% or more and 95% or less. Low magnetic field compared to high field iron loss characteristics Method for producing a high-oriented electrical steel sheet iron loss characteristics. 2. Mo or B is further added as an inhibitor component.
The method for producing a grain-oriented electrical steel sheet having excellent low-field iron loss characteristics as compared with the high-field iron loss characteristics according to claim 1, characterized by containing i, Te, Nb, Sn, and Cr. 3. The high magnetic field according to claim 1, wherein the content of Al and N in the steel slab is 1.67 ≦ Al (wt%) / N (wt%) ≦ 2.18. A method for producing a grain-oriented electrical steel sheet having excellent low-field iron loss characteristics compared to iron loss characteristics. 4. A cold rolling is performed by a tandem rolling mill with a rolling reduction of 8%.
A grain-oriented electrical steel sheet having a low magnetic field iron loss characteristic as compared with the high magnetic field iron loss characteristic according to claim 1, wherein the heat treatment is performed at 0% or more, 95% or less, and at a temperature of 90 ° C or more. Manufacturing method. 5. Cold rolling at a temperature of 120 ° C. or more, 180 ° C.
A method for producing a grain-oriented electrical steel sheet having excellent low-field iron loss characteristics as compared with the high-field iron loss characteristics according to claim 4, wherein the method is performed as follows.